Zonneplan customers billed in 15-minute blocks gain a matching electricity-price sensor in Home Assistant. It uses the quarter-hour prices supplied by Zonneplan rather than the hourly average, giving price-based automations the same time scale as those contracts.
The existing hourly price sensor stays in place. A companion correction updates its value at the start of the hour from prices already fetched, avoiding a wait for the next periodic refresh without adding more requests to Zonneplan.